Method of simultaneous induction heating of complementary sides of two workpieces

ABSTRACT

A method of simultaneous induction heating of two separate workpieces positioned on opposing sides of a double-sided flat inductor assembly with high speed extraction of the inductor assembly after the simultaneous induction heating by magnetic flux coupling from the alternating current source to the inductor assembly.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional application of application Ser. No. 14/661,736,filed Mar. 18, 2015, which application claims the benefit of U.S.Provisional Application No. 61/968,657 filed Mar. 21, 2014, both ofwhich applications are hereby incorporated by reference in theirentireties.

FIELD OF THE INVENTION

The present invention relates to double-sided flat inductor assembliesfor simultaneous induction heating of two separate workpieces positionedon opposing sides of the inductor assembly.

BACKGROUND OF THE INVENTION

It is advantageous in some manufacturing processes to simultaneouslyheat by electric induction two separate workpieces that, for example,may be different from each other and are joined together after heating.

One example of such manufacturing processes is disclosed in U.S. Pat.No. 6,825,450 B2(Ribeiro et al.) where the two separate workpieces arean upper crown part of a piston and the second part is the lower crownpart of a piston that complements the upper part and when joinedtogether form the piston. The upper crown part may also be called thecrown and the lower crown part may also be called the skirt. Thecomplementary sides of the upper and lower crown parts are first heated,for example, by electric induction, and then joined together, forexample, by simultaneously pushing and twisting the complementary sidesof the upper and lower crown parts together. U.S. Pat. No. 6,637,642B1(Lingnau) describes one such joining process. It is advantageous toheat the upper and lower crown parts simultaneously to provide similarheating profiles in both the upper and lower crown parts for thesubsequent welding process that joins the upper and lower crown partstogether.

It is one object of the present invention to provide a double-sided flatinductor assembly for simultaneous induction heating of two separateworkpieces in a manufacturing process.

It is another object of the present invention to provide a double-sidedflat inductor assembly for simultaneous induction heating ofcomplementary sides, or faces of two separate workpieces in amanufacturing process and rapid withdrawal of the inductor assembly awayfrom complementary sides of the two separate workpieces to facilitatejoining of the heated complementary sides.

BRIEF SUMMARY OF THE INVENTION

In one aspect the present invention is a double-sided flat inductorassembly for simultaneous induction heating of two separate workpieceswhen the double-sided flat inductor assembly is positioned between twoseparate workpieces.

In another aspect the present invention is a double-sided flat inductorassembly for simultaneous induction heating of two separate workpieceswhen the double-sided flat inductor assembly is positioned between twoseparate workpieces and an apparatus and method of inserting andextracting the double-sided flat inductor assembly between the twoseparate workpieces.

In another aspect of the present invention is a high speed inductorextraction apparatus and method for positioning an inductor between aworkpiece induction heating position and a workpiece non-interferenceposition.

The above and other aspects of the invention are set forth in thisspecification and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The appended drawings, as briefly summarized below, are provided forexemplary understanding of the invention, and do not limit the inventionas further set forth herein.

FIG. 1(a) is a side elevational view of a first workpiece side of oneexample of a double-sided flat inductor assembly of the presentinvention.

FIG. 1(b) is a cross sectional view of the doubled-sided flat inductorassembly through line 1-1 in FIG. 1(a).

FIG. 2 is a side perspective view of the first workpiece side of thedouble-sided flat inductor assembly shown in FIG. 1(a).

FIG. 3(a) is a side elevational view of a second workpiece side of oneexample of a double-sided flat inductor assembly of the presentinvention.

FIG. 3(b) is a cross sectional view of the doubled-sided flat inductorassembly through line 3-3 in FIG. 3(a).

FIG. 4 is a side perspective view of the second workpiece side of thedoubled-sided flat inductor assembly shown in FIG. 3(a).

FIG. 5 is an end elevational view of the double-sided flat inductorassembly shown in FIG. 1(a) through FIG. 4.

FIG. 6 is a side elevational view of one example of a first workpieceinductor removed from an inductor frame of a double-sided flat inductorassembly of the present invention with the second workpiece inductorpositioned behind the first workpiece inductor.

FIG. 7 is an end elevational view of one example of first and secondworkpiece inductors removed from their inductor frames.

FIG. 8 is a side elevational view of one example of a second workpieceinductor removed from an inductor frame of a double-sided flat inductorassembly of the present invention with the first workpiece inductorpositioned behind the second workpiece inductor.

FIG. 9 is the side perspective view of the first workpiece side of thedouble-sided flat inductor assembly shown in FIG. 2 with a firstworkpiece positioned adjacent to a face of the first workpiece inductorfor induction heating.

FIG. 10 is the side perspective view of the second workpiece side of thedouble-sided flat inductor assembly shown in FIG. 4 with a secondworkpiece positioned adjacent to the face of the second workpieceinductor for induction heating.

FIG. 11 is an end elevational view of one example of the first andsecond sides of a double-sided flat inductor assembly with the first andsecond workpieces respectively positioned adjacent to the faces of thefirst and second workpiece inductors.

FIG. 12(a) and FIG. 12(b) illustrate one example of a first workpieceinductor used in one example of the present invention.

FIG. 12(c) and FIG. 12(d) illustrate one example of a second workpieceinductor used in one example of the present invention.

FIG. 13(a) is a front elevational view of one example of a double-sidedinductor extraction assembly of the present invention for a double-sidedflat inductor assembly.

FIG. 13(b) is a rear elevational view of the double-sided inductorextraction assembly shown in FIG. 13(a).

FIG. 13(c) is a side view of the double-sided inductor extractionassembly shown in FIG. 13(a).

FIG. 13(d) is a front perspective view of the double-sided inductorextraction assembly shown in FIG. 13(a).

FIG. 14(a) is a front elevational view of one example of a double-sidedflat inductor assembly of the present invention attached to thedouble-sided inductor extraction assembly shown in FIG. 13(a) through13(d) in the induction heating position.

FIG. 14(b) is a front perspective view of the double-sided flat inductorassembly attached to the inductor extraction assembly shown in FIG.14(a).

FIG. 14(c) is a side elevational view of the double-sided flat inductorassembly attached to the inductor extraction assembly shown in FIG.14(a).

FIG. 14(d) is a front perspective view of the double-sided flat inductorassembly of the present invention attached to the inductor extractionassembly shown in FIG. 14(a) with first and second workpieces in theinduction heating position.

FIG. 14(e) is a side elevational view of the double-sided flat inductorassembly attached to the inductor extraction assembly shown in FIG.14(a) with a first and second workpiece in the induction heatingposition.

FIG. 15(a) is a front perspective view of a double-sided flat inductorassembly attached to one example of an inductor extraction assembly withthe inductor and extraction assemblies in an induction post-heatextracted position.

FIG. 15(b) is a side elevational view of the double-sided flat inductorassembly attached to the double-sided inductor extraction assembly shownin FIG. 15(a).

FIG. 15(c) is a rear perspective view of the double-sided flat inductorassembly attached to the double-sided inductor extraction assembly shownin FIG. 15(a) with a first and second workpieces.

FIG. 15(d) is a side elevational view of the double-sided flat inductorassembly attached to the double-sided inductor extraction assembly shownin FIG. 15(a) with a first and second workpieces.

FIG. 16 is a diagrammatic electrical circuit representation for theembodiment of the double-sided inductor extraction assembly shown in thefigures.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1(a) through FIG. 12(d) illustrate one embodiment of a double-sidedflat inductor assembly 10 of the present invention comprising firstworkpiece inductor 12 and second workpiece inductor 14 respectivelymounted in first inductor frame 16 and second inductor frame 18. Forconvenience first workpiece 90 a in this example is also referred to asthe skirt and the first workpiece inductor frame 16 is correspondinglylabeled “SKIRT” in some of the figures. Similarly the second workpiece90 b in this example is also referred to as the crown and the secondworkpiece inductor frame 18 is correspondingly labeled “CROWN” in someof the figures. The inductor frames are configured as required for usein a particular application and represented in the figures in oneembodiment.

As shown in one embodiment of the invention, first workpiece inductor 12comprises a first inductor terminal section 12 a (also referred to asskirt inductor foot 12 a), first inductor riser section 12 b (alsoreferred to as skirt inductor leg 12 b) and first inductor coil section12 c (also referred to as skirt coil 12 c).

As shown in one embodiment of the invention, second workpiece inductor14 comprises a second inductor terminal section 14 a (also referred toas crown inductor foot 14 a), second inductor riser section 14 b (alsoreferred to as crown inductor leg 14 b) and second inductor coil section14 c (also referred to as crown coil 14 c).

The first inductor riser section and the second inductor riser sectionare optional in other embodiments and are a means for electricallyinterconnecting the first inductor coil section to the first inductorterminal section, and the second inductor coil section to the secondinductor terminal section, respectively, if there is a requirement tophysically separate the inductor coil sections from the inductorterminal sections.

In this embodiment of the invention first and second inductor coilsections 12 c and 14 c are each shaped as a spirally-coiled inductioncoil (or inductor) that is sometimes referred to as a “pancake” coil.The spacing between turns of the spirally-coiled inductor may vary basedupon the workpiece geometry being heat treated. For example symmetricspacing between all turns of the coil can result in an electromagneticring effect where stronger magnetic fields occur on the inner radialregion of the workpiece face being heat treated compared with the outerradial regions. To compensate in some embodiments of the invention theouter turns may be more closely spaced together than the inner turns.For example in FIG. 1(a) the two outer turns of the first inductor coilsections 12 c′ and 12 c″ are more closely spaced together, and separatedfurther apart from the single inner coil turn 12 c″′ to provide a moreuniform induction heating across the surface (or face) of the workpiecewith reduced sensitivity in coil position relative to the surface of theworkpiece. In other embodiments of the invention other coil turnarrangements can be provided to compensate for selected regions of thefirst or second workpiece in a particular application.

Generally the first inductor coil section and the second inductor coilsection, as disclosed herein, can be referred to as planarly orientedcoil section with the two planarly oriented coil sections being planarlydisposed opposing each other. Deviations from planar, for example, theprofiling described herein are within the terminology of a planarlyoriented coil section. While the embodiment of the inductor coilsections shown in the drawings is circular other configurations can beused in other embodiments of the invention. In other embodiments theentire first workpiece inductor and the entire second workpiece inductorcan be referred to as planarly oriented inductors with the two planarlyoriented inductors being planarly disposed opposing each other.

First and second workpiece inductors are suitably joined togetherelectrically, for example, by brazing to form a series electricalcircuit between the first and second inductor terminal sections 12 a and14 a. First workpiece inductor 12 and second workpiece inductor 14 areconnected electrically in series as diagrammatically shown in FIG. 16for orientation of electrical current through the inductors that allowsmagnetic fluxes generated by each inductor to complement each otherrather than allowing maximum density of alternating current electricalcurrent density to shift towards respected turns of the two inductorsthat results in a dramatic reduction of heating efficiency of respectedareas of the first (skirt) workpiece 90 a and the second (crown)workpiece 90 b.

As shown in FIG. 6 first inductor riser section 12 b includes riser-coilinterface subsection 12 b′. Similarly in FIG. 8 second inductor risersection 14 b includes riser-coil interface subsection 14 b′. In thisembodiment of the invention crown inductor foot 14 a is preferably flushwith the outer surface of skirt inductor foot 12 a on the SKIRT side ofthe inductor assembly to facilitate connections to a single phasealternating current source (not shown in the figures) in someembodiments of the invention.

In this embodiment of the invention the inner coil terminus 12 c′ ofskirt coil 12 c is electrically connected to the inner coil terminus 14c′ of crown coil 14 c as shown in FIGS. 6, 7 and 8 by electricalconnecting element 13, which as mentioned above, can be accomplished bybrazing the inner coil termini of the first and second inductor coils toform a series circuit from the skirt inductor 12 and crown inductor 14between skirt terminal section 12 a and crown terminal section 14 a,which are connected to the outputs of a suitable single phasealternating current power source. Electrically connecting inner coilterminus 12 c′ to inner coil terminus 14 c′ can be accomplished by anysuitable means, for example by brazing (that is, forming a brazed jointbetween the inner coil terminus of the skirt inductor 12 and the innercoil terminus of the crown inductor 14). Alternative means ofelectrically connecting the two inductor coils in series can be, forexample, an electrical conductor suitably connected between the innercoil termini or other coil termini for other inductor coil arrangements.

Suitable middle electrical insulating material 94, for example formedfrom TEFLON®, is positioned as required between: (1) the skirt inductorfoot 12 a, skirt inductor leg 12 b and skirt coil 12 c; and (2) thecrown inductor foot 14 a, crown inductor leg 14 b and crown coil 14 c toprovide a means of electrical isolation between skirt inductor 12 andcrown inductor 14. Any other type of insulating material (dielectric),including air, can be used in other embodiments of the invention toprovided electrical isolation between the skirt and crown inductor.

In this embodiment of the invention first 16 and second 18 inductorframes are each formed from a non-electrically conductive material suchas a phenolic board or a GLASTIC® electrical insulating board.

FIG. 1(b) illustrates in cross section in this embodiment of theinvention, inner skirt and crown concentrators 12 d and 14 drespectively; skirt and crown center plugs 12 e and 14 e respectively;and skirt and crown coils 12 c and 14 c respectively. The inner skirtand crown concentrators as shown in FIG. 1(b) provide maximum magneticintensity on the respective inductor coil section when flush with theheating face (12 c _(face) or 14 c _(face)) of the respective inductorcoil section's inner turn. If the inner face of a particular workpiecesurface to be heat treated is too hot, the inner concentrators can berepositioned or re-sized to reduce the heating efficiency of the innerturn of the inductor coil section to provide a means of controlling theinduction heating process that can rectify heating imbalance between theradial inner and outer workpiece faces. For example one or more of theL-shaped concentrators used in this embodiment can have the top of anL-shaped concentrator shortened adjacent to its respective heating faceto selectively reduce the magnetic intensity for a particular inductionheating application. In other embodiments of the invention theconcentrators can be other than L-shaped to suit a particular inductionheating application.

FIG. 3(b) illustrates in cross section in this embodiment of theinvention, electrical insulating material 92 a and 92 b electricallyseparating skirt inductor foot 12 a from crown inductor foot 14 a. FIG.9 and FIG. 10 also illustrate how in this embodiment of the inventioncrown inductor foot 14 a is flush with the outer surface of skirtinductor foot 12 a on the SKIRT side of the inductor assembly in FIG. 9to facilitate connections to a single phase alternating current sourceeither directly (not shown in the figure) or via an extraction assemblyas described herein while skirt inductor foot 12 a does not extend tothe crown inductor side as indicated by open space 18 b in crowninductor frame 18 in FIG. 10.

Assembly of the first and second workpiece inductors and the first andsecond inductor frames can be, for example, by bolted (or other suitablefastening means) construction.

In this embodiment of the invention FIG. 9 and FIG. 10 illustrate first(skirt) workpiece 90 a in position over skirt coil 12 c for inductionheating of the first workpiece 90 a simultaneously with the inductionheating of the second (crown) workpiece 90 b in position over crown coil14 c, and also in end view in FIG. 11 where the recessed skirt coil andcrown coil are not visible.

In this embodiment of the invention skirt inductor coil 12 c and crowninductor coil 14 c are recessed respectively in skirt inductor frame 16and crown inductor frame 18 as indicated by frame recess regions 16 aand 18 a, for example in FIG. 2 and FIG. 4 respectively.

In some applications of the present invention the geometry of eitherworkpiece can be non-uniform and have substantial changes in mass atvarious radial quadrants of the workpiece. These changes in mass createheat imbalances during heating. To compensate for this, the heatingsurfaces of the respective inductor coil section can be profiled inangular radial quadrants to form a profiled section or regioncorrelating to the different workpiece quadrants of varying mass. Theworkpiece must then be placed in the induction heating position at aspecified orientation to maintain the desired inductor coil section toworkpiece relationship.

Inductor assembly 10 can be connected to an actuator apparatus thatmoves the inductor assembly into the heat position between the first andsecond workpieces (shown in FIG. 11) and a retracted position downwards(in the negative Z-direction) so that facing skirt 90 a and crown 90 bheated surfaces can be simultaneously pushed together (in opposingX-directions) and twisted about the X-axis to join the skirt 90 a andcrown 90 b. Alternatively in other embodiments one of the two workpiecescan remain stationary and the other workpiece can be moved to pushagainst the stationary workpiece.

The actuator apparatus is illustrated in one embodiment of the inventionin FIG. 13(a) through FIG. 13(d) as double-sided inductor extractionassembly 30. Primary magnetic device 32 a is suitably mounted to fixedstructure such as primary mounting plate 81 that can be formed from adielectric. Primary supply electrical conductors 86 a and 86 b are alsomounted to primary mounting plate 81 (via standoff posts 81 a in thisembodiment). Primary supply electrical conductors are illustrated as busbars in the example and can be any type of suitable electricalconductors. Power source cables 82 a and 82 b (three supply and threereturn cables in this embodiment) from a suitable single phasealternating current source are connected respectively to electricalconductors 86 a and 86 b. Power source cables can be any type ofsuitable power source electrical conductors such as bus bars.

Secondary magnetic device 32 b is electrically connected to secondaryoutput electrical conductors 88 a and 88 b. The secondary magneticdevice and secondary output electrical conductors are connected to asuitable extraction actuator 33 which in this embodiment moves thesecondary magnetic device 32 b and secondary output electricalconductors 88 a and 88 b linearly in the plus or minus Z direction asshown in FIG. 13(c) and further described below. In other embodiments ofthe invention the extraction movement may be in another lineardirection, a rotational direction or a combination of linear androtational directions.

FIG. 14(a) through FIG. 14(e) illustrate one example of double-sidedflat inductor assembly 10 electrically connected to the extractionassembly shown in FIG. 13(a) through FIG. 13(d). In this embodimentfirst inductor terminal section 12 a and second inductor terminalsection 14 a are connected respectively to electrically conductors 88 aand 88 b on extraction assembly 30.

Optional cooling fluid medium cables 84 a and 84 b and 84 c and 84 dsupply and return a cooling fluid medium to the skirt and crowninductors via the extraction assembly in this example.

In FIG. 13(a) through FIG. 14(e) extraction assembly 30 and attacheddouble-sided flat inductor assembly 10 are shown in the inductionheating position with the workpieces in place for induction heating asshown in FIGS. 14(d) and 14(e) with the primary magnetic device alignedwith the secondary magnetic device for flux transfer between the supplyand return power magnetic devices and the inductor supply and returnpower magnetic devices. The inductor extraction actuator (not shown inthe figures) moves the secondary magnetic device and secondary outputelectrical conductors with the attached double-sided flat inductorassembly 10 downwards to the inductor assembly (induction post-heat)extracted position where the double-sided flat inductor assembly doesnot interfere with mating of the two workpieces in an industrial processafter being induction heated, for example, when moving the twoworkpieces together.

FIG. 16 is one example of an electrical circuit for the components ofthe double-sided inductor extraction assembly shown in the figures. Inthis embodiment the primary and secondary magnetic devices each comprisetwo electrically isolated magnetic devices. When the extraction assemblyis in the induction heating position and alternating current is suppliedvia power source cables 82 a and 82 b the supply and return electricalcircuit to the double-sided flat inductor assembly is completed by fluxcoupling between the primary magnetic devices and the secondary magneticdevices. When the extraction assembly 30 moves inductor assembly 10 tothe induction post-heat extracted position there is no magnetic fluxcoupling between the primary magnetic devices and the secondary magneticdevices while the inductor assembly is clear of the space between thetwo induction heated workpieces. This method of inductor assemblyextraction provides a high speed method of clearing the space betweenthe two induction heated workpieces while electromagneticallydisconnecting a supply of power to the inductor assembly in comparisonwith mechanical movement of an entire inductor assembly, including, forexample, bus work and power cables connected to a power source. Whenextraction assembly 30 begins to transition inductor assembly 10 fromthe induction heating position to the inductor assembly (inductionpost-heat) extracted position, alternating current output power frompower source PS in FIG. 16 could be turned off and the extractedinductors 12 and 14 on inductor assembly 10 would be powerless duringthe transition between the two positions.

If the first or second workpiece has one or more coil facing protrusionsthat would prevent retraction of the inductor assembly, a depressed coilregion in a coil planar face, such as V-notches 99 shown in FIG. 1(a),FIG. 1(b) and FIG. 2 can be provided in the coil for clearance as theinductor retracts. Depending upon the arc length of the V-notch theworkpiece facing the coil can be rotated in the induction heatingposition during heating to ensure that workpiece surface region facing aV-notch region are sufficiently heated. In the embodiment with arelatively short V-notch region, such as region 99, when the V-notch isless than 90 degrees, the circumferential component of the induced eddycurrent could provide a sufficient heating effect of the workpieceregion that corresponds to the V-notch location, and thereforeeliminating a need for workpiece rotation during heating.

In this example first inductor coil section 12 c has profiled regions,for example, at the top of the coil that are profiled (contoured)regions 99′ in the X-direction (that is, the height of the inductioncoil section). Regions 99′ are raised above the normal face heatingplane of coil section 12 c on either side of V-notches 99 to compensatefor low induced heat in the regions of the coil V-notches. Suchprofiling can be used to conform to the face of the coil sectionadjacent to the face of the workpiece being heated. In other examples ofthe invention the first and second coil sections may be of other shapesand contours to suit the shape of the corresponding first and secondworkpieces to heat each workpiece by proximity heating.

In this embodiment of the invention, in order to improve the heatuniformity in the transition regions 98 (FIG. 1(a) and FIG. 2) wherethere is a transition between the outer turn-to-middle turn andmiddle-turn-to-inner turn of the pair of three turn coils that providesimultaneous heating of the first and second workpieces, there areprofiled regions 98′. In this example, regions 98′ are profiled in theX-direction and raised above the normal face heating plane of the coilsection to compensate for lower heat intensity due to a reduced heatgeneration.

In the above method electromagnetic coupling between primary magneticdevice 32 a and secondary magnetic device 32 b allows the inductor toretract radially (Z-direction) away from the workpieces. For example, inthis embodiment the secondary magnetic device may be slidably mountedadjacent to a stationary primary magnetic device so that the secondarymagnetic device can be slid downwards relative to the primary magneticdevice. There is no physical contact between the primary and secondarydevices which allows the secondary half that forms an electricallyclosed-loop circuit, with the double-sided inductor attached, to bequickly extended to the induction heating position and retracted to theinduction post-heat extraction position. This is diagrammaticallyillustrated in circuit FIG. 16 where the primary circuit is in bold andis connected to the non-bold secondary circuit when there is magneticflux coupling between the primary and secondary magnetic devices. Thismotion allows the inductor assembly to be removed so that an industrialprocess, such as fusing the two workpieces together can occur in afraction of a second after induction heating to minimize heatdissipation due to the combined effect of thermal conduction, thermalradiation and heat convection.

Each primary magnetic device can be any device that creates a magneticflux from an alternating current flow through the device and eachsecondary magnetic device can be any device that magnetically couplesthe primary alternating magnetic flux for power transfer between theprimary and secondary magnetic devices via transformer coupling withoutthere being a physical connection between the primary magnetic devicesand the secondary magnetic devices. For example in one embodiment of theinvention each primary and secondary magnetic device can be two joinedmagnetic C-cores to form a rectangular closed magnetic core with acentral opening in which a portion of electrical conductors 86 a, 86 b,88 a or 88 b are placed so that when alternating current flows throughprimary supply electrical conductors 86 a and 86 b a magnetic flux fieldis created that couples with the corresponding secondary magnetic devicewhen extraction assembly 30 has positioned the inductors in the inductorassembly in the induction heating position. Each primary and secondarymagnetic device may also be referred to as a coil wound core.

The terms skirt and crown are used interchangeably herein with otherpairs of workpieces where it is advantageous to simultaneously inductionheat the two workpieces. Further the process following the simultaneousheating may be joining the opposing faces of the workpieces together,but is not limited to that process as long as the process can benefitfrom the simultaneous induction heating.

The extraction assembly of the present invention may be used with otherconfigurations and quantity of inductors in an induction assembly inindustrial processes where high speed transfer of the inductor assemblyfrom an induction heating position to a workpiece non-interferenceposition where the workpiece can be further processed is desirable.

While the described embodiment of the present example uses a pair ofthree turn coils in series in other embodiments the number of coil turnscan be singular or any multiple number of turns. In other embodimentsthe number of coil turns may be different for each coil in the pair ofcoils.

In the description above, for the purposes of explanation, numerousspecific requirements and several specific details have been set forthin order to provide a thorough understanding of the example andembodiments. It will be apparent however, to one skilled in the art,that one or more other examples or embodiments may be practiced withoutsome of these specific details. The particular embodiments described arenot provided to limit the invention but to illustrate it.

Reference throughout this specification to “one example or embodiment,”“an example or embodiment,” “one or more examples or embodiments,” or“different example or embodiments,” for example, means that a particularfeature may be included in the practice of the invention. In thedescription various features are sometimes grouped together in a singleexample, embodiment, figure, or description thereof for the purpose ofstreamlining the disclosure and aiding in the understanding of variousinventive aspects.

The present invention has been described in terms of preferred examplesand embodiments. Equivalents, alternatives and modifications, aside fromthose expressly stated, are possible and within the scope of theinvention.

1. A method of a simultaneous induction heating of a pair ofcomplementary sides of a first workpiece and a second workpiece, themethod comprising: inserting a double-sided flat inductor assemblybetween the pair of complementary sides of the first workpiece and thesecond workpiece, the double-sided flat inductor assembly comprising: afirst workpiece inductor comprising: a first planarly oriented inductorconfigured for induction heating of a first workpiece face of the firstworkpiece; and a first inductor terminal section electrically connectedto the first planarly oriented inductor; a second workpiece inductorcomprising: a second planarly oriented inductor planarly disposedopposing the first planarly oriented inductor, the second planarlyoriented inductor configured for induction heating of a second workpieceface of the second workpiece, the first workpiece face and the secondworkpiece face respectively forming complementary sides of the first andthe second workpieces; and a second inductor terminal sectionelectrically connected to the second planarly oriented inductor, thesecond planarly oriented inductor and the second inductor terminalsection electrically isolated from the first planarly oriented inductorand the first inductor terminal section; and a first and secondworkpiece inductor electrical connection means for connecting the firstplanarly oriented inductor and the second planarly oriented inductor ina series electrical connection to form a series electrical circuit fromthe first inductor terminal section to the second inductor terminalsection; connecting an inductor power supply and an inductor powerreturn in a secondary magnetic power circuit to the series electricalcircuit to form a combined double-sided flat inductor assembly andsecondary magnetic power circuit; connecting a stationary primarymagnetic power circuit to an alternating current source and positioningthe combined double-sided flat inductor assembly and secondary magneticpower circuit for a magnetic flux transfer established by thealternating current source to the combined double-sided flat inductorassembly for the simultaneous induction heating of the pair ofcomplementary sides of the first and the second workpiece withoutphysical connection between the secondary magnetic power circuit and thestationary primary magnetic power circuit; and extracting the combineddouble-sided flat inductor assembly and secondary magnetic power circuitfrom the stationary primary magnetic power circuit to terminate themagnetic flux transfer and move the combined double-sided flat inductorassembly and secondary magnetic power circuit to clear a space betweenthe pair of complementary sides of the first and the second workpieces.2. The method of claim 1 further comprising disconnecting thealternating current power source from the stationary primary magneticpower circuit prior to extracting the combined double-sided flatinductor assembly and secondary magnetic power circuit from thestationary primary magnetic power circuit.
 3. The method of claim 1wherein extracting the combined double-sided flat inductor assembly andsecondary magnetic power circuit from the stationary primary magneticpower circuit further comprises moving the combined double-sided flatinductor assembly and secondary magnetic power circuit in a lineardirection, rotational direction or a combination of linear androtational directions.
 4. A method of a simultaneous induction heatingof a pair of complementary sides of a first workpiece and a secondworkpiece, the method comprising: inserting a first spiral inductor anda second spiral inductor planarly disposed opposing each other in aseries electrical connection between the pair of complementary sides ofthe first workpiece and the second workpiece; connecting the firstspiral inductor and second spiral inductor to a secondary magnetic powercircuit; magnetically coupling the secondary magnetic power circuit to astationary primary magnetic power circuit connected to an alternatingcurrent power source to establish a magnetic flux field coupling withoutphysical connection between the secondary magnetic power circuit and thestationary primary magnetic power circuit for the simultaneous inductionheating of the pair of complementary sides of the first workpiece andthe second workpiece by the first and second spiral inductorsrespectively; and terminating the magnetic flux field coupling betweenthe secondary magnetic power circuit and the stationary primary magneticpower circuit by extracting the first spiral inductor and second spiralinductor from between the pair of complementary sides of the first andthe second workpieces to clear a space between the pair of complementarysides of the first and the second workpieces.
 5. The method of claim 4further comprising disconnecting the alternating current power sourceprior to extracting the first spiral inductor and the second spiralinductor from between the pair of complementary sides of the first andthe second workpieces.
 6. The method of claim 4 wherein extracting thefirst spiral inductor and the second spiral inductor from between thepair of complementary sides of the first and the second workpiecesfurther comprises moving the first spiral inductor and the second spiralinductor in a linear direction, rotational direction or a combination oflinear and rotational directions.
 7. A method of a simultaneousinduction heating of a pair of complementary sides of a first workpieceand a second workpiece, the method comprising: inserting a first spiralinductor and a second spiral inductor planarly disposed opposing eachother in a series electrical connection between the pair ofcomplementary sides of the first workpiece and the second workpiece;connecting the first spiral inductor and second spiral inductor to asecondary magnetic power circuit; magnetically coupling the secondarymagnetic power circuit to a stationary primary magnetic power circuitconnected to an alternating current power source to establish a magneticflux field coupling without physical connection between the secondarymagnetic power circuit and the stationary primary magnetic power circuitfor the simultaneous induction heating of the pair of complementarysides of the first workpiece and the second workpiece by the first andsecond spiral inductors respectively; disconnecting the alternatingcurrent power source; and terminating the magnetic flux field couplingbetween the secondary magnetic power circuit and the stationary primarymagnetic power circuit by extracting the first spiral inductor andsecond spiral inductor in a radial direction from between the pair ofcomplementary sides of the first and the second workpieces to clear aspace between the pair of complementary sides of the first and thesecond workpieces.